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Dealing with contaminants in biowaste

The presence of unacceptable levels of physical contaminants in biowastes collected and delivered to composting sites is becoming a major concern for the biowaste management industry, says Dr Kiara Zennaro of

The presence of unacceptable levels of physical contaminants in biowastes collected and delivered to composting sites is becoming a major concern for the biowaste management industry.

In particular, when paper and card wastes are commingled with organic wastes (e.g. with garden and food wastes), it is likely that a number of undesirable materials will end up in the organic waste bin which cannot be composted. Many paper and card items contain plastic coatings, metals, inks or other ingredients that tend not to biodegrade enough during composting and are likely to result in low quality compost, not compliant with PAS 100:2011 Specification. Such compost is not acceptable to customers and can damage the environment, animals and our food supply chain.

Over the past few months the ‘paper and card’ issue has led a number of Local Authorities to remove paper and card wastes from the organic waste collections. According to WRAP, 57 Local Authorities in the UK are currently operating organic kerbside collection schemes including card, but it is likely that this number will drop significantly over the next months.

Important drivers for the local authorities’ decision not to collect paper and card alongside organic wastes are the following:

  • As a result of the revised WFD, in future Local Authorities will not be able to count the amounts of waste materials sent to composting towards their recycling performances, unless the resulting compost complies with PAS 100:2011 Specification
  • Defra’s recently published guidance on the waste hierarchy ( highlights that recycling paper back into new paper products is the most environmentally sustainable option.

However, communicating this change of service to the householders without causing a certain level of frustration has turned out to be very challenging. To help Local Authorities to communicate the reason for this change to the householders, WRAP, in conjunction with AfOR, has been developing a ‘change of service’ leaflet, which will clearly convey to the householders the service details and why the service is changing.

It will be available from as an electronic template that can be edited and printed by each Local Authority based on their local collection schemes. The leaflet will highlight to the householders that ‘removing cardboard ensures that garden waste can be turned into compost for a variety of uses, helping the environment’. Most importantly, the leaflet will explain to the householders what they should do with their paper and card wastes. It is likely that the leaflet will be launched in February next year.  

Dr Kiara (Mariachiara) Zennaro, Senior Technical Officer, Association for Organics Recycling,

More information on this issue is available here:

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